Birendra Kumar*, SK Verma, G Ram,HP Singh. 2012 ... - CIMAP Staff

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Temperature Relations for Seed Germination and Vigor in Palmarosa 793 Downloaded by [Birendra Kumar] at 06:15 20 November 2012 determines success or failure of a crop (Hampton & TeKrony 1995). High relative humidity and temperature lower seed viability and vigor. Seed vigor can be influenced by genetic constitution of the variety, environment and nutrition of the mother plant; maturity at harvest; seed size and mass; and mechanical injury, aging, and pathogen factors. Standard germination test results only provide an indication of emergence potential under favorable weather and soil conditions (Sharma 2000). The ability of seed lot to withstand inclement conditions during germination and seedling establishment is conferred by seed vigor. Thus, development of good vigor tests is essential to both commercial growers and seed production companies to ensure high crop performances (Karlovich 1998) and pre- and post-harvest processing for premium quality seed production (Oakley, Kester, & Geneve 2004). Because Palmarosa is seed propagated and commercial growers suffer major losses on account of substandard seeds, it is essential to assess the germination potential and vigor of seeds to ensure a good crop stand and high yield of oil. The present study is a continuation of our earlier study (Verma et al. 2010) to define the temperature and varietal effects and optimize the seed germination potential and seedling vigor under different temperatures for good crop establishment and high productivity. MATERIAL AND METHODS Seed Seeds of Palmarosa varieties, viz., PRC-1, Tripta, Trishna, and Vaishnavi, were collected in November 2009 from plants growing on the experimental farm of the Central Institute of Medicinal and Aromatic Plants (CIMAP), Lucknow, India. These are the improved varieties developed by CIMAP and are cultivated by growers in India. Seeds were removed and stored at 27 ◦ –39 ◦ Cin paper bags until required for experimentation. Germination and Seedling Vigor Tests The experiment was conducted during May–June 2010 at constant temperatures of 20 ◦ ,25 ◦ ,30 ◦ , and 35 ◦ C using daily 16 h light (180 lx)/8 hdark regimes. One hundred seeds were placed per Petri dish (16 cm diameter × 3 cm depth) lined with filter paper (TP) (15 cm diameter) that was soaked with sterile distilled water. The treatments (temperature and variety) were replicated four times. Germination was checked daily and number of normal (bearing both root and shoot) and abnormal (lacking either root or shoot, or stunted growth) seedlings recorded from the first day of counting until the day of maximum seed germination (Kumar, Verma, & Singh 2011). In Palmarosa, there are two types of abnormal seedlings, i.e., shoot without root and root without shoot, which do not exist in other crops (Figure 1).
794 B. Kumar et al. Downloaded by [Birendra Kumar] at 06:15 20 November 2012 FIGURE 1 Shows normal seedlings (right) and abnormal seedlings (left) of the Palmarosa crop. Data on normal seedlings were used for analyses. Germination percentage, seedling vigor index I, and seedling vigor index II were calculated as shown below (ISTA 2010; Kumar, Verma, & Singh 2011; Kumar 2012): Total number of seeds germinated Germination percentage = Total number of seeds in all replicates × 100 From each replication, five normal seedlings were selected randomly at the end of the germination test, and seedling length (root + shoot length) was measured. Mean seedling length (cm) was calculated. The same five seedlings were placed in a paper envelope and dried under shade for 16 h. These dried seedlings were then placed in an oven at 75 ◦ C ± 5 ◦ C for 48 h, after which they were weighed to determine mean seedling dry mass (mg) in each replication. Seedling vigor index I and vigor index II were calculated as follows: Seedling vigor index I = Germiniation (%) × mean seedling length Seedling vigor index II = Germiniation (%) × mean seedling dry mass Statistical Analysis Data were subjected to an analysis of variance (ANOVA) and mean separation. Data were analyzed using GenStat Release 7.21. Least significant difference (LSD) at 5% level was computed for varieties (V) and temperatures (T) when V × T was not significant. When V × T was significant, an LSD to compare V × T means was computed.
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Birendra Kumar*, SK Verma, G Ram,HP Singh. 2012 ... - CIMAP Staff

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